"Sarah Palin knows that it's okay to call someone a retard if like rush you clearly don't mean it which is why we should all come to her defense and say: Sarah Palin is a fucking retard," Colbert quipped.

a very stupid person who acts selfishly, childishly, or immaturely. Does not technically refer to the mentally disabled. When reading this definition, you may think of someone in particular. Chances are, that person fits the criteria of a fucking retard.

Joe Smith: You know that guy who is really stupid and immature?
James Smith: Oh, that fucking retard Allan Evans?
John Smith: Who else would I be talking about!